As a process for producing a corresponding aromatic aldehyde compound by oxidizing a benzyl alcohol compound, there have hitherto been known various methods for oxidation reaction, inclusive of: e.g., oxidation with chromic acid, oxidation with active manganese dioxide, oxidation with dimethyl sulfoxide typified by Swern oxidation, oxidation with an oxoammonium salt compound such as 2,2,6,6-tetramethylpiperidinooxy free radical (TEMPO), and oxidation with a transition metal catalyst such as ruthenium catalyst [JIKKEN KAGAKU KOZA (Experimental Chemistry Course), edited by The Chemical Society of Japan, Organic Synthesis III-Aldehyde•Ketone•Quinone-, 4th edition, MARUZEN Co., Ltd., 1991, Vol. 21, pp. 1-20].
However, in the method for oxidation with chromic acid or active manganese dioxide among the above-mentioned conventional methods, the residual harmful metal compound must be treated after the completion of the reaction. In the method for oxidation with dimethyl sulfoxide, an equivalent or more of an activating agent such as dicyclohexylcarbodiimide (DCC) or acid chloride must be used. Furthermore, in the method for oxidation with an oxoammonium salt compound and the method for oxidation with a transition metal catalyst, an expensive catalyst must be used.
Also, there has been known oxidation with hydrogen peroxide water in the presence of a catalytic amount of sodium tungstate [Tetrahedron Lett., Vo. 39, pp. 7549 (1998)]. However, a problem such as poor reactivity has still been unsolved, with respect to a compound having a substituent such as nitro group.
Furthermore, there has been known a method in which one equivalent of sodium bromate is used in an acetonitrile-water solvent mixture in the presence of 1.5 equivalents of ammonium chloride [J. Chem. Research(s), pp. 100 (1998)]. However, the use of a stoichiometric three-fold amount of an oxidizing agent and a treatment of one equivalent of sodium bromide as a waste are not preferable from industrial point of view.